1. Technical Field
This disclosure relates generally to electronic assembly. More particularly, the present disclosure relates to the assembly method of a die on a substrate or a die on another die as part of a 3D assembly (also called 3D through-silicon vias (“TSV”)) for mass reflow or reflow soldering.
2. Related Art
The dies in a die on die or 3D TSV assembly can be so thin that during the heating or a mass reflow or bonding process the die has a tendency to curl up. This is referred to in the industry as the “potato chip” effect. The “potato chip” effect leaves many bad connections between the base die and the upper die. The current solution for this problem is to use a special nozzle that will enable in situ bonding of the die at the time of placement. The problem with this solution is that often the die needs to be thermally processed before the nozzle can be removed. To accelerate this, the nozzle must be heated and must also be able to be quickly cooled. The entire placement process, therefore, of the die by the nozzle, takes a significant amount of time for each die because the nozzle must remain at the placement location in order to heat and cool the die before moving to pick up another part. Even though progress has been made, the above process of heating and cooling results in a very low placement rate. Moreover, the equipment required to perform these processes is expensive because the accuracy of placement that is required. Therefore, the equipment cost and the time cost (with tact times in the 5 to 60 seconds per die) makes this an expensive process step in a TSV assembly. Additionally, the use of local heating and cooling at the nozzle tip makes it more difficult to reach the required accuracy in the placement and attachment steps.
Thus, a die on die or 3D TSV assembly method and assembly machine compatible with a mass reflow method that alleviates or prevents many of the problems described hereinabove would be well received in the art.